The present invention relates to coal burning apparatus for the generation of steam. It is basic to the operation of boiler-furnace apparatus using coal for the generation of steam that the coal be heated and dried before it is subjected to final combustion. It has also been determined that dust removal apparatus adapted to clean the exhaust gases downstream from the furnace operate more efficiently at high temperatures than when cold.
It is therefore customary to provide an auxiliary heating system for coal burning steam generating apparatus in which a high energy fuel such as gas or oil is used as a fuel to initially heat the entire system whereby combustion of coal may readily be initiated and operation of the various elements of the system may proceed at a high rate of efficiency. Accordingly, the entire system including the boiler, boiler water, ductwork, heating and pulverizing mills for the coal as well as dust collectors for the gas exhausting therefrom are heated until they reach a predetermined operating temperature.
Since such a system requires extensive amounts of high energy fuel as an auxiliary source of heat, it is accordingly expensive to operate. However, it is generally considered necessary to the operation of a coal fired unit since the combustion of pulverized coal with a high moisture content is not possible unless suitably dried.